Arrangement in electronically controlled injection devices and method

ABSTRACT

A device and method for administering one or more injections from an injection cartridge ensures that administration may be performed only if the device is oriented in a predetermined direction. The device features a holding device for the injection cartridge, the holding device having a piston, piston rod, and an electronic control unit that includes a position sensor. The control unit activates the piston and piston rod for administration only if the position sensor determines that the cartridge is oriented in a predetermined direction. The injectable composition may be stored in a multi-chamber injection cartridge, and the device may also reconstitute and remove gases from the composition only if the cartridge is oriented in a predetermined position.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/060,052 filed Apr. 15, 1998, issued Nov. 23, 1999 as U.S. Pat. No.5,989,221. As with U.S. application Ser. No. 09/060,052, thisapplication claims priority from Swedish Patent Application Number9503685-1, filed Oct. 20, 1995, U.S. Provisional Patent Application No.60/005,773, filed Oct. 20, 1995, and PCT Application NumberPCT/SE96/01303, filed Oct. 14, 1996 which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to electronically controlled injectiondevices. More specifically, the invention relates to arrangements inelectronically controlled injection devices, which facilitate a correcthandling of the device when preparing it for the administering of one ormore injections.

BACKGROUND OF THE INVENTION

Electronically controlled injection devices have recently been developedand put on the market. Such devices are generally adapted to utilize aninjection cartridge with one or more chambers, and comprise anelectronic control unit which may be programmed to carry out thenecessary operations for the administering of injections.

Examples of electronically controlled injection devices according to theprior art are described in EP-A-0 164 539 and EP-A-0 293 958. Thesereferences give a good overview of the state of the art in this field.

Electronically controlled injection devices have turned out to have anumber of important advantages, especially in those cases where thepatient has to administer the injections to himself, as is the case inthe ambulatory treatment of diabetics with insulin. The dose to beadministered may be set in advance by the physician, and may even be setat a different value depending on which time of the day the dose is tobe administered. The timer will give a signal when it is time foradministering a dose, and the programmed electric motor will ensure thatthe correct amount is administered. Through modem electronicalengineering and integrated circuitry, the device may be made smallenough to resemble a fountain pen, which can easily be carried in aninside jacket pocket or in a lady's purse.

However, there is still room for improvements in this field. It isdesirable to let the operations for the administering comprise thezeroing of a counter and a display before and after the administering,the removal of entrapped air from the cartridge, the metering out ofdoses of a predetermined magnitude, and the giving of a signal when thecartridge is empty. It may also be desirable to provide a timer to givea signal at the proper time for administering an injection, as well asother functions. The device may often also comprise an electrical motorwhich, on a signal from the control unit, drives a piston rod for apredetermined distance, such that a predetermined dose is administered.Other functions are also possible. This especially applies to thepreparation and readying of the injection device before the firstadministering is to be carried out from a freshly inserted injectioncartridge. These preparation and readying steps include the mixing ofcomponents to reconstitute an injectable composition in the cartridge,when a multi-chamber cartridge is used, the removal of entrapped gasfrom the cartridge, and the zeroing of the counter and/or display unitin the control unit before the first administering. If a multi-chambercartridge is used, the mixing of components to reconstitute aninjectable preparation is also included in the readying steps.

A multi-chamber injection cartridge usually comprises two chamberswithin a cartridge barrel, which chambers are separated by a frontpiston. The front chamber contains a solid component of an injectablecomposition, and is closed at its front end by a closure which may bepierced by an injection needle or cannula. The rear chamber contains aliquid component of an injectable composition and is closed at its rearend by a rear piston. To prepare the cartridge for the administering ofan injectable composition, the rear piston is moved forward. Through theessentially incompressible liquid in the rear chamber, the front pistonwill then also be moved forward, and will at a predetermined positionactivate a bypass connection, such that the liquid in the rear chamberwill be urged over into the front chamber to be mixed with the solidcomponent and form a solution or dispersion to be injected.Multi-chamber injection cartridges comprising more than two chambers arealso known.

The design and function of single-chamber and multi-chamber injectioncartridges are well-known to those skilled in the art, and need not bedescribed here in more detail.

When an injection device is to be readied for the administering ofinjections, an injection cartridge is first positioned and secured in apredetermined location in the device, and a piston rod is brought intocontact with the rear face of the rear piston. By advancement of thepiston rod forward, the cartridge is then readied for administering, asis described in the foregoing, to reconstitute the injectablecomposition. During the reconstitution step, an injection needle may beinserted through the front end closure of the cartridge, to afford aconnection with the outer atmosphere and prevent the build-up of anoverpressure in the cartridge, but this is not strictly necessary atthis stage of the process.

The reconstitution of the injectable composition must often be carriedout under mild conditions, so that sensitive compositions, such asgrowth hormones, are not unduly decomposed. For this, the cartridgeshould be held vertically with its front end pointing upward, and theliquid component should be made to flow calmly into the front chamberwithout any shaking or agitation to aid in the dissolution of the solidcomponent. Other reconstitution positions, such as vertical with thefront end pointing downwards or horizontal, may be utilized, dependingon e.g. distribution of the solids or by-pass design and location.

Generally when mixing components it may also be desirable to securewetting of all solids and all wall surfaces or to impose a certainagitation by turning or rotating the device before subsequent steps inthe administration scheme.

The next step in the readying of the injection device is the removal ofbubbles of air and other gases from the cartridge. This is an importantstep, even though the amount of enclosed gas in modem injectioncartridges is usually not sufficient to cause a health hazard of airembolism if it is accidentally injected. However, as the entrapped gasesare compressible, they serve as a buffer, which may give rise toinaccuracies in the metering out of the liquid composition.

The removal of air and other gases is usually carried out in theconventional way: After having inserted an injection needle through thefront closure of the cartridge (if this has not been done previously),the user holds the injection device vertically with the needle pointingupward, and advances the piston rod forward until no gas, but onlyliquid comes out through the needle.

After the gas has been expelled from the cartridge, the metering scaleand its display is set at zero or some other desired value before theadministering of the injectable composition is started.

In electronically controlled injection devices, the reconstitution ofthe injectable composition, the removal of enclosed air and the zeroingof the metering scale are usually carried out automatically when theuser pushes a start button or the like.

From what has been stated above, it follows that the process of readyingan injection device for the administering of injections is a ratherdelicate process, which demands considerable care from the user.However, this is often forgotten by the user, who usually has no medicaltraining. Thus, the reconstitution of the injectable composition isoften carried out with the cartridge in any arbitrary orientation, whichmay lead to an undesired decomposition of a sensitive composition. Theremoval of air may be forgotten completely, or may be carried cut withthe needle pointing in an unsuitable direction, which may lead to anineffective removal and to spillage of the preparation.

Also during the administration process the device orientation may becritical. Some injection positions may be unsuitable and indicative ofimproper use. Inadvertent administration of multiple doses may takeplace unless the device has been moved or turned between two consecutiveinjections.

Through the present invention, the above shortcomings are eliminated.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an injectiondevice for the administering of one or more injections from an injectioncartridge which is arranged in a holder device and at its rear end isprovided with a piston which be means of a piston rod may be movedforward, the readying of the device for administering after thepositioning of said cartridge and the subsequent administering therefrombeing controlled by an electronic control unit. What characterizes thedevice is that the control unit comprises a position sensor which emitssignals which govern the control unit in such a way that during thereadying of the device, forward movement of the piston rod is only madepossible when the longitudinal axis of the injection cartridge isoriented in a predetermined direction.

Preferably, this predetermined direction is essentially vertical, withthe front end of the cartridge, from which the administering is to takeplace, pointing upward. However, an essentially vertical direction withthe front end of the cartridge pointing downward is also possible.

In a preferred embodiment, the movement of the piston rod is effected bymeans of an electric motor, which is controlled by the control unit.

In a further preferred embodiment, the injection cartridge is amulti-chamber injection cartridge. The readying of the device foradministering one or more injections comprises the reconstitution of aninjectable composition and the removal of gases from said composition,and these processes, through the control by the position sensor, aremade possible only with the logitudinal axis of the cartridge in anessentially vertical orientation with the front end of the cartridgepointing upward.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an embodiment of the instant invention;

FIG. 2 is a schematic of an alternative embodiment of the instantinvention; and

FIG. 3 is a side view of an alternative embodiment of the instantinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawing, the arrangement of the invention is shown schematically.The injection device comprises an injection cartridge 1, which may be ofthe single-chamber or multi-chamber type. Preferably, the cartridge isof the dual-chamber type. The cartridge is provided with a needle orcannula 2 at its front end and with a rear piston 3 at its rear end. Thecartridge contains a liquid component 4, which may fill the cartridgecompletely in the case of a single-chamber cartridge, or may fill a rearchamber in the case of a multi-chamber cartridge. The rear piston 3 isconnected to a piston rod 5, which is actuated by an electric motor 6.The actuation of the motor 6 is governed by signals from the controlunit 7. FIGS. 2 and 3 illustrate an injection device, consistent withthe instant invention, including a multi-chamber container or cartridge20, comprising two or more compartments for components of preparation.The cartridge 20, for example, includes a front chamber or compartment22, a rear chamber or compartment 24, movable pistons 26 separating thecompartments 22 and 24, and a by-pass section 28 for overflow ofcompartment content.

The position or attitude sensor 8 is mechanically connected to thecartridge 1 in such a way that it senses the orientation of thecartridge 1 and sends corresponding signals to the control unit 7. Allthe elements of the injection device are arranged in a suitably shapedhousing or holder device, which is indicated by the dashed line 9.

The injection device further comprises other-elements for fulfillingother functions as desired, such as elements for timing, metering anddisplay. Such elements are known to those skilled in the art, and arenot shown in the drawing.

Position or attitude sensors of the type used in the present inventionare known and may be of different types. It is also known to incorporatesuch sensors in an integrated circuit, for instance from the space andmissile technology. With knowledge of the present invention, there willbe no difficulty for a person skilled in the art to provide a suitableposition sensor and install it properly in an electronic injectiondevice.

For example, attitude sensors of this type are available on the marketas “Non-Mercury Tip-Over Switches” from PEWATRON AG, Wallisellen/Zurich,Switzerland. These switches are available with different operatingangles, i.e. the angle which the switch should be tilted from itsvertical axis to switch from a closed to an open circuit. Other types ofsensors include the well-known mercury switches. These are lesssuitable, however, as it is desirable nowadays to get away from the useof mercury as much as possible in all applications, because of its toxicproperties.

With reference to the drawing, an example of the function of aninjection device of the invention is as follows:

A fresh injection cartridge 1 is placed and secured in a predeterminedlocation in the housing 9, and a needle 2 is inserted through theclosure at its front end. The control unit 7 is then actuated to send asignal to the electrical motor 6 to start the readying of the cartridge1 for the administering of injections.

In a first state, the piston rod 5 is advanced to get into contact withthe rear face of the rear piston 3. The piston 3 will then be urgedfurther forward for the reconstitution of an injectable composition inthe cartridge 1, as has been described in the foregoing. When thereconstitution of the composition is complete, the piston rod has beenmoved forward a given distance, which is sensed by the control unit 7through signals from the motor 6. The motor usually then stops, as theexpulsion of gas from the cartridge does not necessarily have to takeplace immediately after the reconstitution step.

When air or other gases are to be expelled from the cartridge, the useractuates the motor 6 through the control unit 7. The motor 6 is thenkept running and the piston rod 5 is advanced as long as gas is expelledthrough the needle 2, and the movement of the piston rod 5 is stoppedimmediately when liquid starts to flow out from the needle 2. Allgaseous components should now have been expelled from the cartridge 1.

After the zeroing of a metering scale and/or display (not shown), thedevice is ready for administering one or more injections. The dose to beinjected may be set at this time, or it may already have been programmedinto the control unit 7.

During the whole readying process described above, the position orattitude sensor 8 is in mechanical connection with the cartridge 1 andsenses its orientation, usually via the housing 9. It is only when thecartridge is in a predetermined orientation, and preferably then anessentially vertical orientation with the needle pointing upward, thatthe signals from the position sensor 8 will make the control unit 7 sendsignals to the motor 6 which actuate the motor to move the piston rod 5forward. Any important deviation from the vertical position will makethe position sensor send a signal to the control unit 7 to make it stopthe motor 6 and interrupt the readying process. In this way, it isprevented that the readying process takes place with the injectioncartridge in an incorrect orientation. The disadvantages mentioned inthe foregoing are thereby eliminated.

As stated above, an embodiment is also possible wherein the readying ofthe device for injection is carried out with the injection cartridgeoriented in an essentially vertical direction, but with the front end ofthe cartridge pointing downward. The front end of the cartridge shouldbe closed. In this embodiment, an overpressure generated when thesolution is compressed by means of the piston rod 5 will open apressure-sensitive valve in the rear piston, such that the air isexpelled through the rear end of the cartridge. After the air has beenremoved from the cartridge, a needle may be attached to the front end ofthe cartridge, so that an injection may be administered.

After the device has been readied for injection, the control unit 7 willsend a signal to the position or attitude sensor 8 such that the sensoris inactivated. This means that the device can now be used in anyorientation when injections are to be administered.

The design and assembly of the elements in the device of the presentinvention is within the competence of a person skilled in the art, oncesaid person has got an understanding of the inventive idea. The variouselements are commercially available, or can be manufactured in waysknown per se. Also the selection of suitable materials will not pose anygreat problems to one skilled in the art.

Through the present invention, there has been provided a new arrangementin electronically controlled injection devices, where a number ofshortcomings associated with prior art devices have been largelyeliminated. This arrangement will make it easier to avoid errors in thehandling of electronically controlled injection devices.

It is to be noted that the description of the invention in the presentspecification and drawings only serves to exemplify the invention, andnot to restrict it in any way. Variations and modifications of theembodiments disclosed are possible without departing from the scope ofthe claims. It is for example not necessary that the signals from theposition sensor are used by a control unit for actuation of a motor butthey may equally well be used to trigger an alarm or to signal e.g. awarning or instruction message to the operator. Similarly the positionswitch may not only be used during readying of the device but alsoduring injection for sensing improper positions or proper turning of thedevice between injections. For the latter purpose the device shouldinclude means for registration of a sequence of positions, which is alsoof value to monitor an agitation step when desired.

What is claimed is:
 1. A method of administering one or more injectionsfrom an injection cartridge using a holder device having a piston,piston rod and an electronic control unit, the injection cartridgehaving a longitudinal axis, the electronic control unit having aposition sensor, comprising readying the holder device and injecting byforward motion of the piston rod and piston, and whereby the readyingstep includes restricting, by the electronic control unit, the forwardmotion of the piston unless the position sensor determines that thelongitudinal axis of the cartridge is oriented in a predetermineddirection.
 2. The method of administering one or more injectionsaccording to claim 1 whereby the readying step also includes removinggas from the injection cartridge.
 3. The method of administering one ormore injections according to claim 1 wherein the injection cartridge isa multi-chamber cartridge and the readying step also includesreconstituting a injectable composition.
 4. The method of administeringone or more injections according to claim 1 wherein the predetermineddirection is an essentially vertical orientation.